Bottom Slice Flickering

I noticed a slight flickering on the bottom slice during animation. After a little search I noticed that all the other slices animate to 'elCoords.top' and 'elCoords.height' distinct values, but the bottom animates to their sum, which probably, due to rounding, produces slight different values than the other transitions.
So, I thought of this little change to use the same transitions amongst all the slices.
Merge pull request #2 from xpy/patch-1

Very interesting! I wouldn't thought summing the two values would produce such an overhead. I actually always considered this behavior as a side-effect of the bottom slice being the largest one.